Under present technology conditions, a coffer body of a coffer is made from multiple layers of steel plates, which kind of coffer has strong anti-attack ability. However, some regions of the door on which a dial of a combination lock, a cover of the combination lock and a handle are mounted are relatively weak, and are likely to be attacked by criminals. Generally, the criminals may violently attack the coffer from above mentioned weak regions toward inside of the coffer, so as to destroy combination lock mounted on the back side of the door, or the criminals may drill a hole in the door to destroy a position-limiting bolt of the combination lock, or the criminals may drill a hole to the combination lock and apply an inward force through the hole to destroy the combination lock. The above mentioned regions that may be attacked are referred to as “weak regions” of the coffer, and it is easy for a criminal to successfully open the door of the coffer if he/she attacks the coffer from one of the above mentioned “weak regions”.